Wonderwall

Who knew Dr. Hart had such an awesome beach bod underneath that white coat?

Rachel Bilson stunned when she hit the surf in Barbados Wednesday with on-again love Hayden Christensen by her side. The Hart of Dixie actress, 30, rocked a black halter top bikini as she swam with her boyfriend of five years. (Bilson and Christensen, 30--who have dated since 2007--split briefly in 2010, only to reunite a few months later.)

"Rachel and Hayden went into the water and were kissing...They were really sweet together," an eyewitness tells Us Weekly of the actress' beach outing. "At one point, Rachel was playing with her half-sister, Rosemary, and helping her build sand castles."